David Korn’s Korn shell (ksh) lives at http://www.kornshell.com/
I have to admit to a preference for the Bourne shell; partly because of the if/then/else syntax (what is “[[” all about?!), partly because /bin/sh is bourne (or compatible) on all traditional UNIX and Linux (where it’s bash) systems, but ksh is another good, solid shell. The source is also available from AT&T. It’s also a nice interactive shell, in the absence of bash.
There’s also a nice anecdotal story about David Korn – at a launch of Microsoft’s “Services for UNIX” (which actually provides UNIX-like services for Windows), I believe.
You can also see David Korn hanging with KoRn